Many people put their houseplants outdoors for the summer in hopes of rejuvenating them. If done incorrectly, the plants may be ruined.
In fact, if the plant is growing well indoors, there is really no benefit to be gained by taking it outdoors, according to Dr. Charles A. Conover, director of the University of Florida research center, Apopka, which deals with houseplants.
But if the plant is obviously in poor health, due to inadequate light, it often helps to put it on a shaded porch where it will get better light but no sunlight.
A plant growing indoors with rather low light intensity has what is called shade leaves, thinner in the cross section and make maximum use of light energy.
Placing that plant outdoors in full sun, even briefly, will cause severe injury because of cell death caused by high temperatures, Conover says.
Plants grown in full sunlight, or even in a clear glass greenhouse, have sun leaves. They are smaller than shade leaves of the same species and thicker in the cross section.
Both the anatomy and the organnization of a sun leaf prevent injury by intense light since maximum use of the sun's energy is not necessary for growth.
Therefore, when a paant containing primarily sun leaves is placed indoors under low light, it is at a real disadvantage. In most cases, it results in the plant consuming stored food to remain alive, as it cannot produce the food needed because its sun leaves are very inefficient under low light. The plant may die before it loses its sun leaves and gets shade leaves.
What light intensity can the plants tolerate when you put them outdoors? That depends on the level they were receiving indoors. A plant receiving 25 to 75 footcandles indoors can tolerate 1,000 footcandles maximum outdoors, 75 to 150 indoors, 1,500 maximum outdoors; and 150 to 500 indoors, 2,000 maximum outdoors.
Actually, you should seldom place them in full sun, Conover says, and in most instances they need moderate to heavy shade.
Outdoors with higher light intensity and higher respiration rates, the plants will need more frequent watering.
Many gardeners like to move their plants outdoors or indoors for short periods during the summer. If there is much difference in light intensity between the two locations, the plants should be adjusted gradually.
It is acceptable to move a plant from fluorescent light to an east window where it does not receive direct sun: or, move a plant from directly in front of a south window to a terrace where it receives only early morning sun or partial shade all day: and you can move a plant from a shady terrace site to an indoor location near an east or south window.